mm: fix exec activate_mm vs TLB shootdown and lazy tlb switching race

[linux/fpc-iii.git] / fs / gfs2 / log.c

/*
 * Copyright (C) Sistina Software, Inc.  1997-2003 All rights reserved.
 * Copyright (C) 2004-2007 Red Hat, Inc.  All rights reserved.
 *
 * This copyrighted material is made available to anyone wishing to use,
 * modify, copy, or redistribute it subject to the terms and conditions
 * of the GNU General Public License version 2.
 */

#include <linux/sched.h>
#include <linux/slab.h>
#include <linux/spinlock.h>
#include <linux/completion.h>
#include <linux/buffer_head.h>
#include <linux/gfs2_ondisk.h>
#include <linux/crc32.h>
#include <linux/delay.h>
#include <linux/kthread.h>
#include <linux/freezer.h>
#include <linux/bio.h>
#include <linux/blkdev.h>
#include <linux/writeback.h>
#include <linux/list_sort.h>

#include "gfs2.h"
#include "incore.h"
#include "bmap.h"
#include "glock.h"
#include "log.h"
#include "lops.h"
#include "meta_io.h"
#include "util.h"
#include "dir.h"
#include "trace_gfs2.h"

/**
 * gfs2_struct2blk - compute stuff
 * @sdp: the filesystem
 * @nstruct: the number of structures
 * @ssize: the size of the structures
 *
 * Compute the number of log descriptor blocks needed to hold a certain number
 * of structures of a certain size.
 *
 * Returns: the number of blocks needed (minimum is always 1)
 */

unsigned int gfs2_struct2blk(struct gfs2_sbd *sdp, unsigned int nstruct,
                             unsigned int ssize)
{
        unsigned int blks;
        unsigned int first, second;

        blks = 1;
        first = (sdp->sd_sb.sb_bsize - sizeof(struct gfs2_log_descriptor)) / ssize;

        if (nstruct > first) {
                second = (sdp->sd_sb.sb_bsize -
                          sizeof(struct gfs2_meta_header)) / ssize;
                blks += DIV_ROUND_UP(nstruct - first, second);
        }

        return blks;
}

/**
 * gfs2_remove_from_ail - Remove an entry from the ail lists, updating counters
 * @mapping: The associated mapping (maybe NULL)
 * @bd: The gfs2_bufdata to remove
 *
 * The ail lock _must_ be held when calling this function
 *
 */

void gfs2_remove_from_ail(struct gfs2_bufdata *bd)
{
        bd->bd_tr = NULL;
        list_del_init(&bd->bd_ail_st_list);
        list_del_init(&bd->bd_ail_gl_list);
        atomic_dec(&bd->bd_gl->gl_ail_count);
        brelse(bd->bd_bh);
}

/**
 * gfs2_ail1_start_one - Start I/O on a part of the AIL
 * @sdp: the filesystem
 * @wbc: The writeback control structure
 * @ai: The ail structure
 *
 */

static int gfs2_ail1_start_one(struct gfs2_sbd *sdp,
                               struct writeback_control *wbc,
                               struct gfs2_trans *tr)
__releases(&sdp->sd_ail_lock)
__acquires(&sdp->sd_ail_lock)
{
        struct gfs2_glock *gl = NULL;
        struct address_space *mapping;
        struct gfs2_bufdata *bd, *s;
        struct buffer_head *bh;

        list_for_each_entry_safe_reverse(bd, s, &tr->tr_ail1_list, bd_ail_st_list) {
                bh = bd->bd_bh;

                gfs2_assert(sdp, bd->bd_tr == tr);

                if (!buffer_busy(bh)) {
                        if (!buffer_uptodate(bh))
                                gfs2_io_error_bh(sdp, bh);
                        list_move(&bd->bd_ail_st_list, &tr->tr_ail2_list);
                        continue;
                }

                if (!buffer_dirty(bh))
                        continue;
                if (gl == bd->bd_gl)
                        continue;
                gl = bd->bd_gl;
                list_move(&bd->bd_ail_st_list, &tr->tr_ail1_list);
                mapping = bh->b_page->mapping;
                if (!mapping)
                        continue;
                spin_unlock(&sdp->sd_ail_lock);
                generic_writepages(mapping, wbc);
                spin_lock(&sdp->sd_ail_lock);
                if (wbc->nr_to_write <= 0)
                        break;
                return 1;
        }

        return 0;
}


/**
 * gfs2_ail1_flush - start writeback of some ail1 entries 
 * @sdp: The super block
 * @wbc: The writeback control structure
 *
 * Writes back some ail1 entries, according to the limits in the
 * writeback control structure
 */

void gfs2_ail1_flush(struct gfs2_sbd *sdp, struct writeback_control *wbc)
{
        struct list_head *head = &sdp->sd_ail1_list;
        struct gfs2_trans *tr;
        struct blk_plug plug;

        trace_gfs2_ail_flush(sdp, wbc, 1);
        blk_start_plug(&plug);
        spin_lock(&sdp->sd_ail_lock);
restart:
        list_for_each_entry_reverse(tr, head, tr_list) {
                if (wbc->nr_to_write <= 0)
                        break;
                if (gfs2_ail1_start_one(sdp, wbc, tr))
                        goto restart;
        }
        spin_unlock(&sdp->sd_ail_lock);
        blk_finish_plug(&plug);
        trace_gfs2_ail_flush(sdp, wbc, 0);
}

/**
 * gfs2_ail1_start - start writeback of all ail1 entries
 * @sdp: The superblock
 */

static void gfs2_ail1_start(struct gfs2_sbd *sdp)
{
        struct writeback_control wbc = {
                .sync_mode = WB_SYNC_NONE,
                .nr_to_write = LONG_MAX,
                .range_start = 0,
                .range_end = LLONG_MAX,
        };

        return gfs2_ail1_flush(sdp, &wbc);
}

/**
 * gfs2_ail1_empty_one - Check whether or not a trans in the AIL has been synced
 * @sdp: the filesystem
 * @ai: the AIL entry
 *
 */

static void gfs2_ail1_empty_one(struct gfs2_sbd *sdp, struct gfs2_trans *tr)
{
        struct gfs2_bufdata *bd, *s;
        struct buffer_head *bh;

        list_for_each_entry_safe_reverse(bd, s, &tr->tr_ail1_list,
                                         bd_ail_st_list) {
                bh = bd->bd_bh;
                gfs2_assert(sdp, bd->bd_tr == tr);
                if (buffer_busy(bh))
                        continue;
                if (!buffer_uptodate(bh))
                        gfs2_io_error_bh(sdp, bh);
                list_move(&bd->bd_ail_st_list, &tr->tr_ail2_list);
        }

}

/**
 * gfs2_ail1_empty - Try to empty the ail1 lists
 * @sdp: The superblock
 *
 * Tries to empty the ail1 lists, starting with the oldest first
 */

static int gfs2_ail1_empty(struct gfs2_sbd *sdp)
{
        struct gfs2_trans *tr, *s;
        int oldest_tr = 1;
        int ret;

        spin_lock(&sdp->sd_ail_lock);
        list_for_each_entry_safe_reverse(tr, s, &sdp->sd_ail1_list, tr_list) {
                gfs2_ail1_empty_one(sdp, tr);
                if (list_empty(&tr->tr_ail1_list) && oldest_tr)
                        list_move(&tr->tr_list, &sdp->sd_ail2_list);
                else
                        oldest_tr = 0;
        }
        ret = list_empty(&sdp->sd_ail1_list);
        spin_unlock(&sdp->sd_ail_lock);

        return ret;
}

static void gfs2_ail1_wait(struct gfs2_sbd *sdp)
{
        struct gfs2_trans *tr;
        struct gfs2_bufdata *bd;
        struct buffer_head *bh;

        spin_lock(&sdp->sd_ail_lock);
        list_for_each_entry_reverse(tr, &sdp->sd_ail1_list, tr_list) {
                list_for_each_entry(bd, &tr->tr_ail1_list, bd_ail_st_list) {
                        bh = bd->bd_bh;
                        if (!buffer_locked(bh))
                                continue;
                        get_bh(bh);
                        spin_unlock(&sdp->sd_ail_lock);
                        wait_on_buffer(bh);
                        brelse(bh);
                        return;
                }
        }
        spin_unlock(&sdp->sd_ail_lock);
}

/**
 * gfs2_ail2_empty_one - Check whether or not a trans in the AIL has been synced
 * @sdp: the filesystem
 * @ai: the AIL entry
 *
 */

static void gfs2_ail2_empty_one(struct gfs2_sbd *sdp, struct gfs2_trans *tr)
{
        struct list_head *head = &tr->tr_ail2_list;
        struct gfs2_bufdata *bd;

        while (!list_empty(head)) {
                bd = list_entry(head->prev, struct gfs2_bufdata,
                                bd_ail_st_list);
                gfs2_assert(sdp, bd->bd_tr == tr);
                gfs2_remove_from_ail(bd);
        }
}

static void ail2_empty(struct gfs2_sbd *sdp, unsigned int new_tail)
{
        struct gfs2_trans *tr, *safe;
        unsigned int old_tail = sdp->sd_log_tail;
        int wrap = (new_tail < old_tail);
        int a, b, rm;

        spin_lock(&sdp->sd_ail_lock);

        list_for_each_entry_safe(tr, safe, &sdp->sd_ail2_list, tr_list) {
                a = (old_tail <= tr->tr_first);
                b = (tr->tr_first < new_tail);
                rm = (wrap) ? (a || b) : (a && b);
                if (!rm)
                        continue;

                gfs2_ail2_empty_one(sdp, tr);
                list_del(&tr->tr_list);
                gfs2_assert_warn(sdp, list_empty(&tr->tr_ail1_list));
                gfs2_assert_warn(sdp, list_empty(&tr->tr_ail2_list));
                kfree(tr);
        }

        spin_unlock(&sdp->sd_ail_lock);
}

/**
 * gfs2_log_release - Release a given number of log blocks
 * @sdp: The GFS2 superblock
 * @blks: The number of blocks
 *
 */

void gfs2_log_release(struct gfs2_sbd *sdp, unsigned int blks)
{

        atomic_add(blks, &sdp->sd_log_blks_free);
        trace_gfs2_log_blocks(sdp, blks);
        gfs2_assert_withdraw(sdp, atomic_read(&sdp->sd_log_blks_free) <=
                                  sdp->sd_jdesc->jd_blocks);
        up_read(&sdp->sd_log_flush_lock);
}

/**
 * gfs2_log_reserve - Make a log reservation
 * @sdp: The GFS2 superblock
 * @blks: The number of blocks to reserve
 *
 * Note that we never give out the last few blocks of the journal. Thats
 * due to the fact that there is a small number of header blocks
 * associated with each log flush. The exact number can't be known until
 * flush time, so we ensure that we have just enough free blocks at all
 * times to avoid running out during a log flush.
 *
 * We no longer flush the log here, instead we wake up logd to do that
 * for us. To avoid the thundering herd and to ensure that we deal fairly
 * with queued waiters, we use an exclusive wait. This means that when we
 * get woken with enough journal space to get our reservation, we need to
 * wake the next waiter on the list.
 *
 * Returns: errno
 */

int gfs2_log_reserve(struct gfs2_sbd *sdp, unsigned int blks)
{
        int ret = 0;
        unsigned reserved_blks = 7 * (4096 / sdp->sd_vfs->s_blocksize);
        unsigned wanted = blks + reserved_blks;
        DEFINE_WAIT(wait);
        int did_wait = 0;
        unsigned int free_blocks;

        if (gfs2_assert_warn(sdp, blks) ||
            gfs2_assert_warn(sdp, blks <= sdp->sd_jdesc->jd_blocks))
                return -EINVAL;
        atomic_add(blks, &sdp->sd_log_blks_needed);
retry:
        free_blocks = atomic_read(&sdp->sd_log_blks_free);
        if (unlikely(free_blocks <= wanted)) {
                do {
                        prepare_to_wait_exclusive(&sdp->sd_log_waitq, &wait,
                                        TASK_UNINTERRUPTIBLE);
                        wake_up(&sdp->sd_logd_waitq);
                        did_wait = 1;
                        if (atomic_read(&sdp->sd_log_blks_free) <= wanted)
                                io_schedule();
                        free_blocks = atomic_read(&sdp->sd_log_blks_free);
                } while(free_blocks <= wanted);
                finish_wait(&sdp->sd_log_waitq, &wait);
        }
        atomic_inc(&sdp->sd_reserving_log);
        if (atomic_cmpxchg(&sdp->sd_log_blks_free, free_blocks,
                                free_blocks - blks) != free_blocks) {
                if (atomic_dec_and_test(&sdp->sd_reserving_log))
                        wake_up(&sdp->sd_reserving_log_wait);
                goto retry;
        }
        atomic_sub(blks, &sdp->sd_log_blks_needed);
        trace_gfs2_log_blocks(sdp, -blks);

        /*
         * If we waited, then so might others, wake them up _after_ we get
         * our share of the log.
         */
        if (unlikely(did_wait))
                wake_up(&sdp->sd_log_waitq);

        down_read(&sdp->sd_log_flush_lock);
        if (unlikely(!test_bit(SDF_JOURNAL_LIVE, &sdp->sd_flags))) {
                gfs2_log_release(sdp, blks);
                ret = -EROFS;
        }
        if (atomic_dec_and_test(&sdp->sd_reserving_log))
                wake_up(&sdp->sd_reserving_log_wait);
        return ret;
}

/**
 * log_distance - Compute distance between two journal blocks
 * @sdp: The GFS2 superblock
 * @newer: The most recent journal block of the pair
 * @older: The older journal block of the pair
 *
 *   Compute the distance (in the journal direction) between two
 *   blocks in the journal
 *
 * Returns: the distance in blocks
 */

static inline unsigned int log_distance(struct gfs2_sbd *sdp, unsigned int newer,
                                        unsigned int older)
{
        int dist;

        dist = newer - older;
        if (dist < 0)
                dist += sdp->sd_jdesc->jd_blocks;

        return dist;
}

/**
 * calc_reserved - Calculate the number of blocks to reserve when
 *                 refunding a transaction's unused buffers.
 * @sdp: The GFS2 superblock
 *
 * This is complex.  We need to reserve room for all our currently used
 * metadata buffers (e.g. normal file I/O rewriting file time stamps) and 
 * all our journaled data buffers for journaled files (e.g. files in the 
 * meta_fs like rindex, or files for which chattr +j was done.)
 * If we don't reserve enough space, gfs2_log_refund and gfs2_log_flush
 * will count it as free space (sd_log_blks_free) and corruption will follow.
 *
 * We can have metadata bufs and jdata bufs in the same journal.  So each
 * type gets its own log header, for which we need to reserve a block.
 * In fact, each type has the potential for needing more than one header 
 * in cases where we have more buffers than will fit on a journal page.
 * Metadata journal entries take up half the space of journaled buffer entries.
 * Thus, metadata entries have buf_limit (502) and journaled buffers have
 * databuf_limit (251) before they cause a wrap around.
 *
 * Also, we need to reserve blocks for revoke journal entries and one for an
 * overall header for the lot.
 *
 * Returns: the number of blocks reserved
 */
static unsigned int calc_reserved(struct gfs2_sbd *sdp)
{
        unsigned int reserved = 0;
        unsigned int mbuf;
        unsigned int dbuf;
        struct gfs2_trans *tr = sdp->sd_log_tr;

        if (tr) {
                mbuf = tr->tr_num_buf_new - tr->tr_num_buf_rm;
                dbuf = tr->tr_num_databuf_new - tr->tr_num_databuf_rm;
                reserved = mbuf + dbuf;
                /* Account for header blocks */
                reserved += DIV_ROUND_UP(mbuf, buf_limit(sdp));
                reserved += DIV_ROUND_UP(dbuf, databuf_limit(sdp));
        }

        if (sdp->sd_log_commited_revoke > 0)
                reserved += gfs2_struct2blk(sdp, sdp->sd_log_commited_revoke,
                                          sizeof(u64));
        /* One for the overall header */
        if (reserved)
                reserved++;
        return reserved;
}

static unsigned int current_tail(struct gfs2_sbd *sdp)
{
        struct gfs2_trans *tr;
        unsigned int tail;

        spin_lock(&sdp->sd_ail_lock);

        if (list_empty(&sdp->sd_ail1_list)) {
                tail = sdp->sd_log_head;
        } else {
                tr = list_entry(sdp->sd_ail1_list.prev, struct gfs2_trans,
                                tr_list);
                tail = tr->tr_first;
        }

        spin_unlock(&sdp->sd_ail_lock);

        return tail;
}

static void log_pull_tail(struct gfs2_sbd *sdp, unsigned int new_tail)
{
        unsigned int dist = log_distance(sdp, new_tail, sdp->sd_log_tail);

        ail2_empty(sdp, new_tail);

        atomic_add(dist, &sdp->sd_log_blks_free);
        trace_gfs2_log_blocks(sdp, dist);
        gfs2_assert_withdraw(sdp, atomic_read(&sdp->sd_log_blks_free) <=
                             sdp->sd_jdesc->jd_blocks);

        sdp->sd_log_tail = new_tail;
}


static void log_flush_wait(struct gfs2_sbd *sdp)
{
        DEFINE_WAIT(wait);

        if (atomic_read(&sdp->sd_log_in_flight)) {
                do {
                        prepare_to_wait(&sdp->sd_log_flush_wait, &wait,
                                        TASK_UNINTERRUPTIBLE);
                        if (atomic_read(&sdp->sd_log_in_flight))
                                io_schedule();
                } while(atomic_read(&sdp->sd_log_in_flight));
                finish_wait(&sdp->sd_log_flush_wait, &wait);
        }
}

static int ip_cmp(void *priv, struct list_head *a, struct list_head *b)
{
        struct gfs2_inode *ipa, *ipb;

        ipa = list_entry(a, struct gfs2_inode, i_ordered);
        ipb = list_entry(b, struct gfs2_inode, i_ordered);

        if (ipa->i_no_addr < ipb->i_no_addr)
                return -1;
        if (ipa->i_no_addr > ipb->i_no_addr)
                return 1;
        return 0;
}

static void gfs2_ordered_write(struct gfs2_sbd *sdp)
{
        struct gfs2_inode *ip;
        LIST_HEAD(written);

        spin_lock(&sdp->sd_ordered_lock);
        list_sort(NULL, &sdp->sd_log_le_ordered, &ip_cmp);
        while (!list_empty(&sdp->sd_log_le_ordered)) {
                ip = list_entry(sdp->sd_log_le_ordered.next, struct gfs2_inode, i_ordered);
                list_move(&ip->i_ordered, &written);
                if (ip->i_inode.i_mapping->nrpages == 0)
                        continue;
                spin_unlock(&sdp->sd_ordered_lock);
                filemap_fdatawrite(ip->i_inode.i_mapping);
                spin_lock(&sdp->sd_ordered_lock);
        }
        list_splice(&written, &sdp->sd_log_le_ordered);
        spin_unlock(&sdp->sd_ordered_lock);
}

static void gfs2_ordered_wait(struct gfs2_sbd *sdp)
{
        struct gfs2_inode *ip;

        spin_lock(&sdp->sd_ordered_lock);
        while (!list_empty(&sdp->sd_log_le_ordered)) {
                ip = list_entry(sdp->sd_log_le_ordered.next, struct gfs2_inode, i_ordered);
                list_del(&ip->i_ordered);
                WARN_ON(!test_and_clear_bit(GIF_ORDERED, &ip->i_flags));
                if (ip->i_inode.i_mapping->nrpages == 0)
                        continue;
                spin_unlock(&sdp->sd_ordered_lock);
                filemap_fdatawait(ip->i_inode.i_mapping);
                spin_lock(&sdp->sd_ordered_lock);
        }
        spin_unlock(&sdp->sd_ordered_lock);
}

void gfs2_ordered_del_inode(struct gfs2_inode *ip)
{
        struct gfs2_sbd *sdp = GFS2_SB(&ip->i_inode);

        spin_lock(&sdp->sd_ordered_lock);
        if (test_and_clear_bit(GIF_ORDERED, &ip->i_flags))
                list_del(&ip->i_ordered);
        spin_unlock(&sdp->sd_ordered_lock);
}

void gfs2_add_revoke(struct gfs2_sbd *sdp, struct gfs2_bufdata *bd)
{
        struct buffer_head *bh = bd->bd_bh;
        struct gfs2_glock *gl = bd->bd_gl;

        bh->b_private = NULL;
        bd->bd_blkno = bh->b_blocknr;
        gfs2_remove_from_ail(bd); /* drops ref on bh */
        bd->bd_bh = NULL;
        bd->bd_ops = &gfs2_revoke_lops;
        sdp->sd_log_num_revoke++;
        if (atomic_inc_return(&gl->gl_revokes) == 1)
                gfs2_glock_hold(gl);
        set_bit(GLF_LFLUSH, &gl->gl_flags);
        list_add(&bd->bd_list, &sdp->sd_log_le_revoke);
}

void gfs2_glock_remove_revoke(struct gfs2_glock *gl)
{
        if (atomic_dec_return(&gl->gl_revokes) == 0) {
                clear_bit(GLF_LFLUSH, &gl->gl_flags);
                gfs2_glock_queue_put(gl);
        }
}

void gfs2_write_revokes(struct gfs2_sbd *sdp)
{
        struct gfs2_trans *tr;
        struct gfs2_bufdata *bd, *tmp;
        int have_revokes = 0;
        int max_revokes = (sdp->sd_sb.sb_bsize - sizeof(struct gfs2_log_descriptor)) / sizeof(u64);

        gfs2_ail1_empty(sdp);
        spin_lock(&sdp->sd_ail_lock);
        list_for_each_entry(tr, &sdp->sd_ail1_list, tr_list) {
                list_for_each_entry(bd, &tr->tr_ail2_list, bd_ail_st_list) {
                        if (list_empty(&bd->bd_list)) {
                                have_revokes = 1;
                                goto done;
                        }
                }
        }
done:
        spin_unlock(&sdp->sd_ail_lock);
        if (have_revokes == 0)
                return;
        while (sdp->sd_log_num_revoke > max_revokes)
                max_revokes += (sdp->sd_sb.sb_bsize - sizeof(struct gfs2_meta_header)) / sizeof(u64);
        max_revokes -= sdp->sd_log_num_revoke;
        if (!sdp->sd_log_num_revoke) {
                atomic_dec(&sdp->sd_log_blks_free);
                /* If no blocks have been reserved, we need to also
                 * reserve a block for the header */
                if (!sdp->sd_log_blks_reserved)
                        atomic_dec(&sdp->sd_log_blks_free);
        }
        gfs2_log_lock(sdp);
        spin_lock(&sdp->sd_ail_lock);
        list_for_each_entry(tr, &sdp->sd_ail1_list, tr_list) {
                list_for_each_entry_safe(bd, tmp, &tr->tr_ail2_list, bd_ail_st_list) {
                        if (max_revokes == 0)
                                goto out_of_blocks;
                        if (!list_empty(&bd->bd_list))
                                continue;
                        gfs2_add_revoke(sdp, bd);
                        max_revokes--;
                }
        }
out_of_blocks:
        spin_unlock(&sdp->sd_ail_lock);
        gfs2_log_unlock(sdp);

        if (!sdp->sd_log_num_revoke) {
                atomic_inc(&sdp->sd_log_blks_free);
                if (!sdp->sd_log_blks_reserved)
                        atomic_inc(&sdp->sd_log_blks_free);
        }
}

/**
 * log_write_header - Get and initialize a journal header buffer
 * @sdp: The GFS2 superblock
 *
 * Returns: the initialized log buffer descriptor
 */

static void log_write_header(struct gfs2_sbd *sdp, u32 flags)
{
        struct gfs2_log_header *lh;
        unsigned int tail;
        u32 hash;
        int op_flags = REQ_PREFLUSH | REQ_FUA | REQ_META | REQ_SYNC;
        struct page *page = mempool_alloc(gfs2_page_pool, GFP_NOIO);
        enum gfs2_freeze_state state = atomic_read(&sdp->sd_freeze_state);
        lh = page_address(page);
        clear_page(lh);

        gfs2_assert_withdraw(sdp, (state != SFS_FROZEN));

        tail = current_tail(sdp);

        lh->lh_header.mh_magic = cpu_to_be32(GFS2_MAGIC);
        lh->lh_header.mh_type = cpu_to_be32(GFS2_METATYPE_LH);
        lh->lh_header.__pad0 = cpu_to_be64(0);
        lh->lh_header.mh_format = cpu_to_be32(GFS2_FORMAT_LH);
        lh->lh_header.mh_jid = cpu_to_be32(sdp->sd_jdesc->jd_jid);
        lh->lh_sequence = cpu_to_be64(sdp->sd_log_sequence++);
        lh->lh_flags = cpu_to_be32(flags);
        lh->lh_tail = cpu_to_be32(tail);
        lh->lh_blkno = cpu_to_be32(sdp->sd_log_flush_head);
        hash = gfs2_disk_hash(page_address(page), sizeof(struct gfs2_log_header));
        lh->lh_hash = cpu_to_be32(hash);

        if (test_bit(SDF_NOBARRIERS, &sdp->sd_flags)) {
                gfs2_ordered_wait(sdp);
                log_flush_wait(sdp);
                op_flags = REQ_SYNC | REQ_META | REQ_PRIO;
        }

        sdp->sd_log_idle = (tail == sdp->sd_log_flush_head);
        gfs2_log_write_page(sdp, page);
        gfs2_log_flush_bio(sdp, REQ_OP_WRITE, op_flags);
        log_flush_wait(sdp);

        if (sdp->sd_log_tail != tail)
                log_pull_tail(sdp, tail);
}

/**
 * gfs2_log_flush - flush incore transaction(s)
 * @sdp: the filesystem
 * @gl: The glock structure to flush.  If NULL, flush the whole incore log
 *
 */

void gfs2_log_flush(struct gfs2_sbd *sdp, struct gfs2_glock *gl,
                    enum gfs2_flush_type type)
{
        struct gfs2_trans *tr;
        enum gfs2_freeze_state state = atomic_read(&sdp->sd_freeze_state);

        down_write(&sdp->sd_log_flush_lock);

        /* Log might have been flushed while we waited for the flush lock */
        if (gl && !test_bit(GLF_LFLUSH, &gl->gl_flags)) {
                up_write(&sdp->sd_log_flush_lock);
                return;
        }
        trace_gfs2_log_flush(sdp, 1);

        if (type == SHUTDOWN_FLUSH)
                clear_bit(SDF_JOURNAL_LIVE, &sdp->sd_flags);

        sdp->sd_log_flush_head = sdp->sd_log_head;
        tr = sdp->sd_log_tr;
        if (tr) {
                sdp->sd_log_tr = NULL;
                tr->tr_first = sdp->sd_log_flush_head;
                if (unlikely (state == SFS_FROZEN))
                        gfs2_assert_withdraw(sdp, !tr->tr_num_buf_new && !tr->tr_num_databuf_new);
        }

        if (unlikely(state == SFS_FROZEN))
                gfs2_assert_withdraw(sdp, !sdp->sd_log_num_revoke);
        gfs2_assert_withdraw(sdp,
                        sdp->sd_log_num_revoke == sdp->sd_log_commited_revoke);

        gfs2_ordered_write(sdp);
        lops_before_commit(sdp, tr);
        gfs2_log_flush_bio(sdp, REQ_OP_WRITE, 0);

        if (sdp->sd_log_head != sdp->sd_log_flush_head) {
                log_flush_wait(sdp);
                log_write_header(sdp, 0);
        } else if (sdp->sd_log_tail != current_tail(sdp) && !sdp->sd_log_idle){
                atomic_dec(&sdp->sd_log_blks_free); /* Adjust for unreserved buffer */
                trace_gfs2_log_blocks(sdp, -1);
                log_write_header(sdp, 0);
        }
        lops_after_commit(sdp, tr);

        gfs2_log_lock(sdp);
        sdp->sd_log_head = sdp->sd_log_flush_head;
        sdp->sd_log_blks_reserved = 0;
        sdp->sd_log_commited_revoke = 0;

        spin_lock(&sdp->sd_ail_lock);
        if (tr && !list_empty(&tr->tr_ail1_list)) {
                list_add(&tr->tr_list, &sdp->sd_ail1_list);
                tr = NULL;
        }
        spin_unlock(&sdp->sd_ail_lock);
        gfs2_log_unlock(sdp);

        if (type != NORMAL_FLUSH) {
                if (!sdp->sd_log_idle) {
                        for (;;) {
                                gfs2_ail1_start(sdp);
                                gfs2_ail1_wait(sdp);
                                if (gfs2_ail1_empty(sdp))
                                        break;
                        }
                        atomic_dec(&sdp->sd_log_blks_free); /* Adjust for unreserved buffer */
                        trace_gfs2_log_blocks(sdp, -1);
                        log_write_header(sdp, 0);
                        sdp->sd_log_head = sdp->sd_log_flush_head;
                }
                if (type == SHUTDOWN_FLUSH || type == FREEZE_FLUSH)
                        gfs2_log_shutdown(sdp);
                if (type == FREEZE_FLUSH)
                        atomic_set(&sdp->sd_freeze_state, SFS_FROZEN);
        }

        trace_gfs2_log_flush(sdp, 0);
        up_write(&sdp->sd_log_flush_lock);

        kfree(tr);
}

/**
 * gfs2_merge_trans - Merge a new transaction into a cached transaction
 * @old: Original transaction to be expanded
 * @new: New transaction to be merged
 */

static void gfs2_merge_trans(struct gfs2_sbd *sdp, struct gfs2_trans *new)
{
        struct gfs2_trans *old = sdp->sd_log_tr;

        WARN_ON_ONCE(!test_bit(TR_ATTACHED, &old->tr_flags));

        old->tr_num_buf_new     += new->tr_num_buf_new;
        old->tr_num_databuf_new += new->tr_num_databuf_new;
        old->tr_num_buf_rm      += new->tr_num_buf_rm;
        old->tr_num_databuf_rm  += new->tr_num_databuf_rm;
        old->tr_num_revoke      += new->tr_num_revoke;
        old->tr_num_revoke_rm   += new->tr_num_revoke_rm;

        list_splice_tail_init(&new->tr_databuf, &old->tr_databuf);
        list_splice_tail_init(&new->tr_buf, &old->tr_buf);

        spin_lock(&sdp->sd_ail_lock);
        list_splice_tail_init(&new->tr_ail1_list, &old->tr_ail1_list);
        list_splice_tail_init(&new->tr_ail2_list, &old->tr_ail2_list);
        spin_unlock(&sdp->sd_ail_lock);
}

static void log_refund(struct gfs2_sbd *sdp, struct gfs2_trans *tr)
{
        unsigned int reserved;
        unsigned int unused;
        unsigned int maxres;

        gfs2_log_lock(sdp);

        if (sdp->sd_log_tr) {
                gfs2_merge_trans(sdp, tr);
        } else if (tr->tr_num_buf_new || tr->tr_num_databuf_new) {
                gfs2_assert_withdraw(sdp, test_bit(TR_ALLOCED, &tr->tr_flags));
                sdp->sd_log_tr = tr;
                set_bit(TR_ATTACHED, &tr->tr_flags);
        }

        sdp->sd_log_commited_revoke += tr->tr_num_revoke - tr->tr_num_revoke_rm;
        reserved = calc_reserved(sdp);
        maxres = sdp->sd_log_blks_reserved + tr->tr_reserved;
        gfs2_assert_withdraw(sdp, maxres >= reserved);
        unused = maxres - reserved;
        atomic_add(unused, &sdp->sd_log_blks_free);
        trace_gfs2_log_blocks(sdp, unused);
        gfs2_assert_withdraw(sdp, atomic_read(&sdp->sd_log_blks_free) <=
                             sdp->sd_jdesc->jd_blocks);
        sdp->sd_log_blks_reserved = reserved;

        gfs2_log_unlock(sdp);
}

/**
 * gfs2_log_commit - Commit a transaction to the log
 * @sdp: the filesystem
 * @tr: the transaction
 *
 * We wake up gfs2_logd if the number of pinned blocks exceed thresh1
 * or the total number of used blocks (pinned blocks plus AIL blocks)
 * is greater than thresh2.
 *
 * At mount time thresh1 is 1/3rd of journal size, thresh2 is 2/3rd of
 * journal size.
 *
 * Returns: errno
 */

void gfs2_log_commit(struct gfs2_sbd *sdp, struct gfs2_trans *tr)
{
        log_refund(sdp, tr);

        if (atomic_read(&sdp->sd_log_pinned) > atomic_read(&sdp->sd_log_thresh1) ||
            ((sdp->sd_jdesc->jd_blocks - atomic_read(&sdp->sd_log_blks_free)) >
            atomic_read(&sdp->sd_log_thresh2)))
                wake_up(&sdp->sd_logd_waitq);
}

/**
 * gfs2_log_shutdown - write a shutdown header into a journal
 * @sdp: the filesystem
 *
 */

void gfs2_log_shutdown(struct gfs2_sbd *sdp)
{
        gfs2_assert_withdraw(sdp, !sdp->sd_log_blks_reserved);
        gfs2_assert_withdraw(sdp, !sdp->sd_log_num_revoke);
        gfs2_assert_withdraw(sdp, list_empty(&sdp->sd_ail1_list));

        sdp->sd_log_flush_head = sdp->sd_log_head;

        log_write_header(sdp, GFS2_LOG_HEAD_UNMOUNT);

        gfs2_assert_warn(sdp, sdp->sd_log_head == sdp->sd_log_tail);
        gfs2_assert_warn(sdp, list_empty(&sdp->sd_ail2_list));

        sdp->sd_log_head = sdp->sd_log_flush_head;
        sdp->sd_log_tail = sdp->sd_log_head;
}

static inline int gfs2_jrnl_flush_reqd(struct gfs2_sbd *sdp)
{
        return (atomic_read(&sdp->sd_log_pinned) +
                atomic_read(&sdp->sd_log_blks_needed) >=
                atomic_read(&sdp->sd_log_thresh1));
}

static inline int gfs2_ail_flush_reqd(struct gfs2_sbd *sdp)
{
        unsigned int used_blocks = sdp->sd_jdesc->jd_blocks - atomic_read(&sdp->sd_log_blks_free);

        if (test_and_clear_bit(SDF_FORCE_AIL_FLUSH, &sdp->sd_flags))
                return 1;

        return used_blocks + atomic_read(&sdp->sd_log_blks_needed) >=
                atomic_read(&sdp->sd_log_thresh2);
}

/**
 * gfs2_logd - Update log tail as Active Items get flushed to in-place blocks
 * @sdp: Pointer to GFS2 superblock
 *
 * Also, periodically check to make sure that we're using the most recent
 * journal index.
 */

int gfs2_logd(void *data)
{
        struct gfs2_sbd *sdp = data;
        unsigned long t = 1;
        DEFINE_WAIT(wait);
        bool did_flush;

        while (!kthread_should_stop()) {

                /* Check for errors writing to the journal */
                if (sdp->sd_log_error) {
                        gfs2_lm_withdraw(sdp,
                                         "GFS2: fsid=%s: error %d: "
                                         "withdrawing the file system to "
                                         "prevent further damage.\n",
                                         sdp->sd_fsname, sdp->sd_log_error);
                }

                did_flush = false;
                if (gfs2_jrnl_flush_reqd(sdp) || t == 0) {
                        gfs2_ail1_empty(sdp);
                        gfs2_log_flush(sdp, NULL, NORMAL_FLUSH);
                        did_flush = true;
                }

                if (gfs2_ail_flush_reqd(sdp)) {
                        gfs2_ail1_start(sdp);
                        gfs2_ail1_wait(sdp);
                        gfs2_ail1_empty(sdp);
                        gfs2_log_flush(sdp, NULL, NORMAL_FLUSH);
                        did_flush = true;
                }

                if (!gfs2_ail_flush_reqd(sdp) || did_flush)
                        wake_up(&sdp->sd_log_waitq);

                t = gfs2_tune_get(sdp, gt_logd_secs) * HZ;

                try_to_freeze();

                do {
                        prepare_to_wait(&sdp->sd_logd_waitq, &wait,
                                        TASK_INTERRUPTIBLE);
                        if (!gfs2_ail_flush_reqd(sdp) &&
                            !gfs2_jrnl_flush_reqd(sdp) &&
                            !kthread_should_stop())
                                t = schedule_timeout(t);
                } while(t && !gfs2_ail_flush_reqd(sdp) &&
                        !gfs2_jrnl_flush_reqd(sdp) &&
                        !kthread_should_stop());
                finish_wait(&sdp->sd_logd_waitq, &wait);
        }

        return 0;
}